1. Field of the Invention
The present invention relates to an improvement in an apparatus such as a camera which makes it possible to automatically start reusing a partially used film of a film cartridge at the position of an unused frame.
2. Description of Related Art
Cameras which can make a magnetic recording on a film have heretofore been known. A film cartridge for use with such a camera is provided with an index which indicates the state of exposure of the film accommodated in the film cartridge, i.e., whether the film is an unexposed film, a completely exposed film or a partially exposed film. Accordingly, it has been proposed to provide a camera which, if a film cartridge having a partially exposed film is loaded into the camera, automatically winds the film up to the position of the first unexposed frame on the basis of information obtained from the index and information magnetically recorded on the partially exposed film.
In the aforesaid conventional example, the operation of advancing the film up to the position of the first unexposed frame is carried out by magnetically reproducing magnetic recorded information written to the film and determining whether each frame of the film is an unexposed frame or an exposed frame. In the case of this kind of film, a signal to be used for such a determination is commonly reproduced by a magnetic reproducing circuit having a large amplification degree because the density of the magnetic layer provided on the film is low.
In the case of such a magnetic reproducing method, the influence of external magnetic noise which enters the camera from the surroundings is not ignorable, and if a magnetic head picks up such noise during magnetic reproduction, the camera may become unable to discriminate between the noise and a magnetic signal written to the film itself and erroneously determine whether a particular frame of the film is an unexposed frame or an exposed frame. This leads to the problem that an exposed frame is again exposed.